A Fairfax County Democratic Committee sign reminds people to update their addresses for their voter registration, on Oct. 2, 2016, in Tysons Corner, Va. (Alex Wong/Getty Images)

Welcome back to The Monkey Cage’s weekly presentation of Founding Principles, short videos designed to explain American government and how it works — in theory and in practice. The first five episodes looked at the basic structure of the government created by the U.S. Constitution — the separation of powers between its levels and across its branches, and then at each of those branches in turn: Congress, the presidency and the judiciary. Then we looked at how “we the people” are connected to that government — through public opinion, the media, and, of course, elections. In the last episode, we began to think about how House, Senate and presidential elections work.

This week’s episode asks: Who are the voters? What guides their choices?

You might be forgiven for thinking that elections are like the Super Bowl. The contenders go back and forth. There is a compelling narrative — the underdog triumphs! The big lead is blown! Key moments get played over and over, including “game changers” where what seemed inevitable suddenly became impossible, and vice versa.

This is how the news media often cover elections, especially with the rise of the Internet and social media. As John Sides and Lynn Vavreck noted in their book on the 2012 election, one journalist identified 68 episodes that were described as “game changers” that year. The term was used in the media almost 20,000 times in the 10 months before Election Day that November.

Nevertheless, the game itself — the actual gap between Barack Obama and Mitt Romney that year — didn’t move around much. That makes sense when we think about what we know about how people actually decide how they will vote. One key is how party identification shapes a voter’s worldview, as we saw in the 2016 election.

Still, certain issues do have a big effect on election results — and the most prominent is the economy. National economic performance is a very strong predictor of whether voters will be for or against the incumbent party. That shows us that voting is mostly retrospective. It looks backward at performance, rather than forward at campaign promises and party platforms.

The episode covers all this, and more — then finishes up by thinking about voter turnout. The constitutional amendments added after the Bill of Rights are mostly about expanding citizenship and voting rights. But not all who can vote actually do — especially in midterm elections. Why? That’s an important question, if we think of voting as an assertion of citizenship, a barometer measuring the very health of our democracy.